The correct answer is: (3) A-II, B-I, C-IV, D-III
(A) Mathematical expression for rate of reaction - (II) Rate law:
The rate law is a mathematical expression that relates the rate of a chemical reaction to the concentrations of reactants. So, the rate law is indeed the mathematical expression for the rate of reaction.
(B) Rate of reaction for a zero-order reaction is equal to - (I) Rate constant:
In a zero-order reaction, the rate of reaction is equal to the rate constant (k). In a zero-order reaction, the rate of the reaction is independent of the concentration of the reactants. The rate equation for a zero-order reaction is typically expressed as:
Rate = k
Where:
- Rate is the rate of the reaction.
- k is the rate constant, which is a constant value at a given temperature.
In contrast to first-order and second-order reactions, where the rate of the reaction depends on the concentration of one or more reactants raised to the power of 1 or 2, respectively, zero-order reactions have a constant rate regardless of changes in reactant concentrations.
(C) Unit of rate constant for a zero-order reaction is the same as that of - (IV) Rate of reaction:
The unit of rate constant for a zero-order reaction is the same as the unit of the rate of reaction. This is because the rate of a zero-order reaction is independent of the concentration of the reactant(s).
The general rate equation for a zero-order reaction is:
\[ \text{Rate} = k \]
where \( k \) is the rate constant.
The units of the rate of a reaction are typically moles per liter per second (M/s). Therefore, the units of the rate constant for a zero-order reaction are also M/s.
Here are some examples of units for the rate constant of a zero-order reaction:
- \( \text{M/s} \)
- \( \text{mol L}^{-1} \text{ s}^{-1} \)
- \( \text{mmol L}^{-1} \text{ s}^{-1} \)
- \( \mu\text{mol L}^{-1} \text{ s}^{-1} \)
It is important to note that the units of the rate constant will vary depending on the units used for the concentration and time. For example, if the concentration is expressed in mol/dm³ and the time is expressed in minutes, then the units of the rate constant will be \( \text{mol dm}^{-3} \text{ min}^{-1} \).
(D) Order of a complex reaction is determined by - (III) Order of the slowest step:
For complex reactions that occur through multiple elementary steps, the overall rate of the reaction is often determined by the slowest (rate-determining) step. So, the order of a complex reaction is indeed determined by the order of the slowest step.
Therefore, the correct matching is: (3) A-II, B-I, C-IV, D-III
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